This invention relates to the two stroke engine, mainly an improvement to reduce the high pollution contained in the exhaust, a dominant weakness the traditional two stroke engine has ever embraced. Particularly, it requires no mixing of engine oil to be added during the refilling with gasoline.
Please refer to FIGS. 1 and 2. They are schematic diagrams showing the general two stroke engine where the cylinder 10 provides an intake way 11 and an exhaust way 12 at the opposed direction. A piston 13 has a piston ring 131 installed on the piston crown to choke the gasoline mixture with the cylinder 10. A connecting rod 14 has a piston pin 15 at one end being locked in the piston 13 and the other end connected to the crankshaft 17 within the crank case 16. When the piston 13 comes up and compresses the gasoline mixture in the combustion chamber of cylinder 10, an explosion follows as the spark plug 18 ignites the compressed gasoline mixture, and the piston 13 is thus moved down. When the piston 13 moves down to the exhaust way 12, the exhaust flows out right at this moment. The flowing of the exhaust through the exhaust way 12 will create a venturi effect and a negative pressure in the combustion chamber in the cylinder 10 as compared with the preset pressure in the crank case 16, the gasoline mixture will be sucked into the cylinder 10 through the intake way 11 (with one way valve), and the piston 13 and the connecting rod 14 will continue to move up by the rotary force of the crankshaft 17 to proceed the second compress ion and explosion and so on. It is easy to learn that the two stroke engine is simple in construction, less loss in power, benefiting greater horsepower and long service time. In down movement of the piston 13, because there exist an intake way 11 and an exhaust way 12 on both sides, there is no way to reserve the engine oil in the crank case 16. Therefore, the engine oil has to be added to the gasoline while refilling where the engine oil will form a lubricating film along the piston after explosion, resulted in an incomplete combustion, a culprit for pollution.
FIG. 3 shows a schematic diagram of a four stroke engine, where the engine oil is stored in the crank case 16, and intake way 20 and the exhaust way 21 are moved to the top of the cylinder 10. When the piston 13 moves upward in the cylinder 10, it is not necessary for the piston 13 to bring up the engine oil to the intake way 20 and exhaust way 21, the four stroke engine entails no engine oil to be mixed with the gasoline, a complete combustion is therefore achieved and the exhaust is more environmental-friendly. However, in the four stroke engine, the intake valve 20 and the exhaust valve 21 need to be controlled by the camshaft (not shown), inefficiency caused by a complicated mechanism, heavy consumption of energy and less horsepower is unavoidable.
Comparing the merits and demerits between the two stroke engine and the four stroke engine, after many years"" endeavor to the research and development, tests and experiments, the inventor has come up a practicable two stroke engine in which all merits are conserved and all demerits are removed in an attempt to upgrade the motorcycle industry and to solve the pollution the motorcycle yields.
The invention mainly employs a sleeve piston structure over the main piston which serves to block the engine oil from arousing to the intake way and exhaust way along the piston wall while the piston moves up. It therefore requires no adding engine oil to the gasoline to ensure a clean exhaust pursuant to the emission standard set forth by environmental protection requirements.